Lesson three C + + data types

Speak the keywords, identifiers, and operators of the C + + language before explaining the data type.

Key Words

Keyword is a C + + predefined words, we define variables are not easy to use, the common keywords are: ( understand )

Asm	Double	New	Switch
Auto	Else	operator	Template
Break	Enum	Private	This
Case	extern	Protected	Throw
Catch	Float	Public	Try
Char	For	Return	typedef
Class	Friend	Register	Union
Const	Goto	Short	Unsigned
Continue	If	Signed	Virtual
Default	Inline	sizeof	void
Delete	Int	Static	Volatile
Do	Long	Struck	While

　Identifier

An identifier is a sequence of characters used to identify variables, functions, data types, and so on.

Identifiers can consist of uppercase letters, lowercase letters, underscores (_), and numeric 0~9, but must be preceded by a lower case letter or an underscore (_).

For example, name and name represent two different identifiers.

operator

Operators are symbols used to perform operations, such as + 、-、 *,/, and so on.

Next is the point: * * *

Basic data type Detailed

Id	Category	Key words	Description
1	Data type	bool	Basic Type--Boolean type
2	Data type	Char	Basic type--character type
3	Data type	wchar_t	Basic type--wide character type
4	Data type	Double	Basic type--solid type
5	Data type	Float	Basic type--floating-point type
6	Data type	Int	Basic type--integral type
7	Data type	Long	Basic type--long integer type
8	Data type	Short	Basic type--short integer type
9	Data type	Signed	Basic type--Signed integral type
10	Data type	Unsigned	Basic type--unsigned integral type
11	Data type	False	Boolean type--False value
12	Data type	True	Boolean Type--truth
13	Data type	Enum	base class Type-enum type
14	Data type	Union	Base class type-union type
15	Data type	struct	base class type-struct type
16	Data type	TypeName	This keyword is used to represent a common type when defining a template.
17	Data type	typedef	Alias--Used to alias data type
18	Data type	sizeof	Length calculation-The length of bytes occupied by the calculation type
19	Condition control	Switch	Switch Branch statement
20	Condition control	Case	Switch Branch statement--Conditional judgment
21st	Condition control	Break	Conditional interrupts
22	Condition control	Default	Switch Branch statement--default branch
23	Condition control	Continue	Skip Continue
24	Condition control	Do	Cycle
25	Condition control	Else	Branch
26	Condition control	For	Cycle
27	Condition control	Goto	Jump
28	Condition control	If	Branch
29	Condition control	While	Cycle
30	Condition control	Return	Return
31	Semantic retouching	Auto	Declaring a variable's lifetime is automatic, and the variable defined in any class, struct, enumeration, union, and function is not treated as a global variable, whereas a variable defined in a function is considered a local variable. This keyword doesn't write much, because all variables are auto by default.
32	Semantic retouching	Const	The const-modified items are protected against accidental changes and can improve the robustness of the program. A modifier function parameter (non-intrinsic type), which is a const reference pass. The decorated return value (the return value is a pointer type) can only be assigned to variables of the same type. Modifier variables Modifier pointer variable
33	Semantic retouching	extern	Declare and reference this variable as an external variable that exists in a file in the project.
34	Semantic retouching	Friend	Declare a friend function or class.
35	Semantic retouching	Inline	The declaration defines an inline function, which embeds the called code into the main function at compile time.
36	Semantic retouching	Private	access Rights : the class private function and the data member's label. Private members are accessible only to member functions of the class itself. Inherit permissions : All member access permissions for the parent class become private in the subclass.
37	Semantic retouching	Public	access Rights : class public functions and data members are marked. can be accessed by object or class name. inherited permissions : The access rights of the parent class members are unchanged in the subclass, and are still their original permissions.
38	Semantic retouching	Protected	access Rights : class-protected functions and data members are marked. Protected members are accessible only to member functions of the class and to member functions of their derived classes. inherited permissions : The public member access rights of the parent class become protected in the subclass, and the protected members and private members of the parent class maintain the same permissions on the child class permissions.
39	Semantic retouching	Register	This keyword commands the compiler to increase efficiency by having variables in the CPU internal registers as much as possible, rather than through memory addressing.
40	Semantic retouching	Static	Process-oriented static keyword To define a static global variable : The scope is in this file and is not visible in other files. Uninitialized static global variables are automatically initialized and automatically initialized to 0 by the program. Static global variables allocate memory in the global data area. Defining static Local variables The scope is a function in this file, initialized only once, and the value is persisted to the next call when the function is called multiple times, until the new value is assigned next time. Static local variables are typically initialized at the declaration and, if not explicitly initialized, are automatically initialized to 0 by the program. Static local variables allocate memory in the global data area. Defining static Functions Only visible in the file it declares. Object-oriented static keyword Defining static data members for a class Static data members are treated as members of the class, all objects share access, and their values can be updated. Static data members comply with PUBLIC,PROTECTED,PRIVATE access rules like normal data members. Static data members are stored in the global data area. Static data members are defined when space is allocated. The static data member initialization format is as follows: Data type >< class name >::< static data member name >=< value Two ways to access static data members: Class object name >.< static data member name or Class type name >::< static data member name > static data members advantages (compared to global variables) Static data members do not enter the program's global namespace, so there is no possibility of conflicts with other global names in the program. Information hiding can be implemented. A static data member can be a private member, while a global variable cannot. Defining static functions for a class Static functions are treated as members of the class, and all objects share access. You need to add the static keyword when declaring inside a class without adding the static keyword when you define it outside the class. A non-static member function can arbitrarily access static member functions and static data members. It does not have the this pointer, it cannot access non-static data members that belong to a class object, and cannot access a non-static member function, it can only invoke the rest of the static member functions. Call Format: Class name >::< static member function name > (parameter table)

Lesson three C + + data types